The human B-lymphotropic virus (HBLV) is a novel herpesvirus recently isolated from fresh human peripheral blood mononuclear cells. It is hypothesized that HBLV may play a role in some lymphoproliferative and immune abnormalities of man. As a recent virus isolate, little is known of the biological properties and cytopathology of HBLV, and few reagents are available to investigators in the field. The development of a battery of monoclonal antibodies directed against HBLV-induced polypeptides is necessary to facilitate studies aimed at elucidating the role of this virus in human, including its putative pathologic role. In addition to the potential usefulness of such antibodies to research laboratories, they should prove useful in the development of diagnostic tests employed by clinical laboratories. The Phase I effort will concentrate on developing procedures for generating monoclonal antibodies directed against HBLV structural and non-structural antigens. Antibodies produced in mice will be characterized as to their localization in infected cells and the specificity of their reactivity with distinct virus-encoded polypeptides. The Phase II effort will concentrate on producing a battery of such antibodies and developing assay kits for diagnosing infection by HBLV.